Download presentation

Presentation is loading. Please wait.

Published byLily Cooke Modified over 2 years ago

1
1 EE365 Sequential-circuit analysis

2
2 Clocked synchronous seq. circuits A.k.a. “state machines” Use edge-triggered flip-flops All flip-flops are triggered from the same master clock signal, and therefore all change state together Feedback sequential circuits –No explicit flip-flops; state stored in feedback loops –Example: edge-triggered D flip-flop itself (4 states) –Sections 7.9, 7.10 (advanced courses)

3
3 State-machine structure (Mealy) typically edge-triggered D flip-flops output depends on state and input

4
4 State-machine structure (Moore) output depends on state only typically edge-triggered D flip-flops

5
5 State-machine structure (pipelined) Often used in PLD-based state machines. –Outputs taken directly from flip-flops, valid sooner after clock edge. –But the “output logic” must determine output value one clock tick sooner (“pipelined”).

6
6 Notation, characteristic equations Q means “the next value of Q.” “Excitation” is the input applied to a device that determines the next state. “Characteristic equation” specifies the next state of a device as a function of its excitation. S-R latch: Q = S + R´ · Q Edge-triggered D flip-flop: Q = D

7
7 State-machine analysis steps Assumption: Starting point is a logic diagram. 1. Determine next-state function F and output function G. 2a. Construct state table –For each state/input combination, determine the excitation value. –Using the characteristic equation, determine the corresponding next-state values (trivial with D f-f’s). 2b. Construct output table –For each state/input combination, determine the output value. (Can be combined with state table.) 3. (Optional) Draw state diagram

8
8 Example state machine

9
9 Excitation equations

10
10 Transition equations Excitation equations Characteristic equations Substitute excitation equations into characteristic equations

11
11 Transition and state tables transition table state table state/output table (transition equations) (output equation)

12
12 State diagram Circles for states Arrows for transitions (note output info)

13
13 Modified state machine Moore machine MAXS = Q0 Q1 MAXS

14
14 Updated state/output table, state diagram

15
15 Timing diagram for state machine Not a complete description of machine behavior

Similar presentations

OK

1 Sequential logic networks I. Motivation & Examples Output depends on current input and past history of inputs. “State” embodies all the information.

1 Sequential logic networks I. Motivation & Examples Output depends on current input and past history of inputs. “State” embodies all the information.

© 2017 SlidePlayer.com Inc.

All rights reserved.

Ads by Google

Ppt on mineral and power resources Ppt on effects of world war 1 Ppt on ram and rom computer Ppt on business etiquette in india Ppt on natural numbers symbol Ppt on oracle database Ppt on fibonacci numbers stocks Ppt on cross docking advantages Ppt on content development tools Ppt on applied operations research va